Heya Tangled! As most of us know here (and you seem to have figured out), It is WAY easier to tell someone to let go than to actually do it. Unfortunately, the only way for the heart to catch up to the head is one-hell-of-a-lot-of-grieving and this takes a long time (probably more time than your friends or you realize)
When I went through this kind of loss, I didn't have any friends who had been through this. Consequently my friends were as much help to me as your friends seem to be to you. This is not their fault; they just can't understand.
The pain of true grieving is so intense that many folks just skip it. They do this through alcohol/drugs/eating/another-relationship/sex/porn/gaming. You apparently are not one that is going to take a short cut. Congrats and condolences!!!
It can help to count the days since you ended the relationship . . . a bit like alcoholics count days of sobriety. Each day of painful grieving you do is one day closer to being healed. The best book I ever found on grieving was How to Survive the Loss of a Love. It is a quick, fun and helpful read.
Keep posting and take care of yourself and your kids. You are doing something of amazing courage and strength. We all here can give you electronic ovations, hugs or shoulder to cry one whenever you need it!!